This invention relates to a filter press and to a method of operating a filter press.
A filter press of the kind to which this invention relates and which is adapted to separate liquid and solid components of a feed stream comprises a plurality of filter units. Each filter unit comprises a filter plate and a pair of flexible filter elements in the form of filter cloths or filter fabrics respectively at opposite sides of the filter plate. The filter units are arranged in tandem, i.e. in parallel planes, in a frame intermediate a fixed support and a displaceable end plate. The displaceable end plate is operatively connected to displacement means--generally in the form of a hydraulic ram--selectively to close the filter units against one another (the closed condition of the filter press) and to part the various filter units from another (the open condition of the filter press). In its closed condition, the pressure to which the filter units are subjected on account of the ram seals the filter units off against one another.
Each filter plate has, along its opposed sides, depressions. Its filter elements are spanned over those depressions. In use, when under pressure, the filter elements will be pressed against, to be supported by, the bottoms of those depressions.
Conduits are provided respectively to charge the filter press, more specifically to introduce the feed stream in the form of a slurry or suspension or the like under pressure into envelopes formed intermediate the pairs of adjacent filter elements. The liquid component flows under pressure through the filter elements into the depressions, i.e. intermediate the respective filter plates and their filter elements, and passages are provided to exhaust such liquid. The solids component of the feed stream builds up ultimately to form a cake intermediate each pair of filter elements. At that stage, charging of the filter press is interrupted, and the displacement means is operated to part the plates and the cakes are removed.
If desired, the press can be washed or rinsed, generally by providing sprayers spraying a liquid--normally water--onto the upstream faces of the filter elements.
The displacement means is operated again and the filter units are moved against each other and compressed against one another intermediate the fixed end support and the movable end plate.